A transmissive liquid crystal display device, which includes a liquid crystal display panel on which images and text information are to be displayed, includes an illuminating device for projecting light onto a back face of the liquid crystal display panel (a so-called backlight). An edge-light illuminating device is well known as this kind of illuminating device, which includes a plate-shaped light guide plate made from a transparent material such as an acrylic resin, and a light source such as a cold cathode fluorescent tube and a light-emitting diode that is disposed along an edge face of the light guide plate (see PTL 1). A thin profile of the edge-light illuminating device having this configuration can be advantageously achieved more easily than illuminating devices of other types, and thus the edge-light illuminating devices are used favorably.
Among the edge-light illuminating devices, an edge-light illuminating device including a light-emitting diode as a light source has the advantages of a long life and a high luminous efficiency, which has been receiving widespread attention in recent years (see PTL 2).
The edge-light illuminating device includes a reflection sheet disposed on a back face of the light guide plate as disclosed in PTLs 1 and 2. The reflection sheet defines a resin foam sheet having the shape corresponding to the shape of the light guide plate, and is arranged to reflect to return light that leaks out of the back face of the light guide plate.